An investigation has been made of improving beam quality of a high power diode pumped solid state rod laser. It was determined that the beam quality is limited by aberrations present in the medium, which may be due to mode-medium effects in the Yb:YAG laser. A diffractive optics propagation model was developed to predict the phase distortions present on the laser wavefront at the resonator mirror. Resonator mirrors were then fabricated with the proper correction applied to correct the distorted wavefront. The beam quality improved from M2 = 2.0 to M2 =1.4.
A power scaling investigation of a Yb:YAG rod laser configured with a stable resonator is described. A dual laser rod architecture was chosen to minimize thermal birefringence. An investigation of the medium was carried out by measuring the aberrations during lasing conditions. The limitation of beam quality seems to be due to aberrations related to the mode-medium interaction. The experiments measured the severity of the aberrations and the Zernike coefficients were determined. A simple model provided some insight into the operation of the laser. It has been noted that under certain conditions, spherical aberration can improve beam quality.
A scaleable diode end-pumping technology for high-average- power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M2 equals 2.4) q-switched operation has also been demonstrated at over 180 W of average output power. More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M2 value of 13.5 at an optical-to-optical conversion efficiency of 27.5%2. With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M2 less than 2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes. (2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods.
We have investigated the process of UV laser evaporation of diamond-like carbon films on metallic and semiconducting alloys. High purity targets in vacuum were irradiated with a pulsed KrF excimer laser beam (248 nm). Adhesion of diamond-like carbon films to several materials was improved by applying in situ germanium interlayers. Various process parameters were varied to determine the optimum conditions for deposition. The diamond-like films and germanium interlayers were structurally characterized by inelastic light scattering and scanning electron microscopy. Mechanical properties such as indenter hardness and friction coefficient were also measured. Preliminary results indicate that films deposited at low substrate temperature and high laser fluence have superior mechanical properties.
Conference Committee Involvement (9)
Solid State Lasers XXX: Technology and Devices
6 March 2021 | Online Only, California, United States
Solid State Lasers XXIX: Technology and Devices
4 February 2020 | San Francisco, California, United States
Solid State Lasers XXVIII: Technology and Devices
5 February 2019 | San Francisco, California, United States
Solid State Lasers XXVII: Technology and Devices
29 January 2018 | San Francisco, California, United States
Solid State Lasers XXVI: Technology and Devices
30 January 2017 | San Francisco, California, United States
Solid State Lasers XXV: Technology and Devices
15 February 2016 | San Francisco, California, United States
Solid State Lasers XXIV: Technology and Devices
8 February 2015 | San Francisco, California, United States
Solid State Lasers XXIII: Technology and Devices
2 February 2014 | San Francisco, California, United States
Solid State Lasers XXII: Technology and Devices
3 February 2013 | San Francisco, California, United States